Information scrambling refers to the spread of quantum information due to complex dynamics in a quantum system. The original information tossed into such a scrambling system is not accessible via a local measurement, and hence, the quantum information is hidden from a local observer.
Quantum information theoretic aspects of the scrambling dynamics were initially studied in the context of black hole physics, where the black hole dynamics is modeled by a Haar random unitary evolution to reflect a nature of black hole as a fast scrambler [1]}, [2]}, [3]}, [4]} (see Refs. [5]}, [6]}, [7]} for preceding works in the context of quantum information theory).
Since then, the information scrambling has attracted huge attention in a wide range of disciplines: quantum gravity, quantum many-body physics, quantum information, and many others. Along the progress in understanding complex quantum dynamics, various diagnostic tools of scrambling have been proposed and scrutinized. Among others, out-of-time ordered correlators (OTOCs) provide a way to quantify the scrambling-ness by capturing operator growth due to the associated quantum dynamics [8]}, [9]}, [3]}, [11]}.
